Modal Analysis of All-Walls Longitudinally Corrugated Rectangular Waveguides Using Asymptotic Corrugations Boundary Conditions

The asymptotic corrugations boundary conditions (ACBCs) are used together with classical theory of vector potentials and an innovative combination of matrix systems to analyze rectangular waveguides having all four walls being longitudinally (axially) corrugated. One matrix system is composed of the ACBCs of two opposite walls, while the other comprises those of the other pair of corrugated walls. A transcendental characteristic equation is derived, from which the modal dispersion diagram can be obtained, for all three modal wave-tyoes: fast space, slow surface, and evanescent waves. From the formulation, analytical modal field functions in closed form are also acquired. Results of dispersion graphs and modal field distributions generated by this method are compared favorably with those obtained by a commercial full-wave solver.